AP Biology
10 reactions
convert
glucose (6C) to
2 pyruvate (3C)
produces:
4 ATP & 2 NADH
consumes:
2 ATP
net:
2 ATP & 2 NADH
glucoseC-C-C-C-C-C
fructose-1,6bPP-C-C-C-C-C-C-P
DHAPP-C-C-C
G3PC-C-C-P
pyruvateC-C-C
OverviewATP2
ADP2
ATP4
ADP4
NAD+2
2
2Pi
2Pi
2H
AP Biology 2006-2007
Cellular Respiration
Stage 2 & 3:
Oxidation of Pyruvate
Krebs Cycle
AP Biology
pyruvate CO2
Glycolysis is only the start
Glycolysis
Pyruvate has more energy to yield
3 more C to strip off (to oxidize)
if O2 is available, pyruvate enters mitochondria
enzymes of Krebs cycle complete the full
oxidation of sugar to CO2
2x6C 3C
glucose pyruvate
3C 1C
AP Biology
Cellular respiration
AP Biology
intermembranespace inner
membrane
outermembrane
matrix
cristae
Mitochondria — Structure Double membrane energy harvesting organelle
smooth outer membrane
highly folded inner membrane
cristae
intermembrane space
fluid-filled space between membranes
matrix
inner fluid-filled space
DNA, ribosomes
enzymes
free in matrix & membrane-bound
mitochondrialDNA
What cells would have a lot of mitochondria?
AP Biology
Mitochondria – Function
What does this tell us about
the evolution of eukaryotes?
Endosymbiosis!
Dividing mitochondria
Who else divides like that?
Advantage of highly folded inner
membrane?
More surface area for membrane-
bound enzymes & permeases
Membrane-bound proteins
Enzymes & permeases
Oooooh!Form fits function!
bacteria!
AP Biology
pyruvate acetyl CoA + CO2
Oxidation of pyruvate
NAD
3C 2C 1C[2x ] Pyruvate enters mitochondrial matrix
3 step oxidation process
releases 2 CO2 (count the carbons!)
reduces 2 NAD 2 NADH (moves e-)
produces 2 acetyl CoA
Acetyl CoA enters Krebs cycle
Wheredoes theCO2 go?Exhale!
AP Biology
Pyruvate oxidized to Acetyl CoA
Yield = 2C sugar + NADH + CO2
reduction
oxidation
Coenzyme APyruvate
Acetyl CoA
C-C-CC-CCO2
NAD+
2 x [ ]
AP Biology
Krebs cycle
aka Citric Acid Cycle
in mitochondrial matrix
8 step pathway
each catalyzed by specific enzyme
step-wise catabolism of 6C citrate molecule
Evolved later than glycolysis
does that make evolutionary sense?
bacteria 3.5 billion years ago (glycolysis)
free O2 2.7 billion years ago (photosynthesis)
eukaryotes 1.5 billion years ago (aerobic
respiration = organelles mitochondria)
1937 | 1953
Hans Krebs1900-1981
AP Biology
4C
6C
4C
4C
4C
2C
6C
5C
4C
CO2
CO2
citrate
acetyl CoA
Count the carbons!3Cpyruvate
x2
oxidationof sugars
This happens
twice for each
glucose
molecule
AP Biology
4C
6C
4C
4C
4C
2C
6C
5C
4C
CO2
CO2
citrate
acetyl CoA
Count the electron carriers!3Cpyruvate
reductionof electron
carriers
This happens
twice for each
glucose
molecule x2
CO2
NADH
NADH
NADH
NADH
FADH2
ATP
AP Biology
So we fully
oxidized
glucose
C6H12O6
CO2
& ended up
with 4 ATP!
Whassup?
What’s the point?
AP Biology
Krebs cycle
produces large
quantities of
electron carriers
NADH
FADH2
go to Electron
Transport Chain!
Electron Carriers = Hydrogen Carriers
What’s so important about
electron carriers?
H+
H+H+
H+
H+ H+
H+H+H+
ATP
ADP
+ Pi
AP Biology
Energy accounting of Krebs cycle
Net gain = 2 ATP
= 8 NADH + 2 FADH2
1 ADP 1 ATPATP
2x
4 NAD + 1 FAD 4 NADH + 1 FADH2
pyruvate CO2
3C 3x 1C
AP Biology
Value of Krebs cycle?
If the yield is only 2 ATP then how was the
Krebs cycle an adaptation?
value of NADH & FADH2
electron carriers & H carriers
reduced molecules move electrons
reduced molecules move H+ ions
to be used in the Electron Transport Chain
like $$in the bank
AP Biology 2006-2007
What’s thepoint?
The pointis to make
ATP!
ATP
AP Biology
H+
H+H+
H+
H+ H+
H+H+
H+
And how do we do that?
ATP
But… Have we done that yet?
ADP P+
ATP synthase
set up a H+ gradient
allow H+ to flow
through ATP synthase
powers bonding
of Pi to ADP
ADP + Pi ATP
AP Biology 2006-2007
NO!The final chapter to my story is
next!Any Questions?